Field of the Invention
The present invention relates to a magnetoresistance effect element.
Priority is claimed on Japanese Patent Application No. 2016-192010, filed Sep. 29, 2016, the content of which is incorporated herein by reference,
Description of Related Art
A giant magnetoresistance (GMR) element that is made of a multilayer film of a ferromagnetic layer and a non-magnetic layer and a tunnel magnetoresistance (TMR) element that uses an insulating layer (a tunnel barrier layer or a barrier layer) for a non-magnetic layer are known (JP5586028B, US2013-0221461-A, APPLIED PHYSICS LETTERS 96, 212505 (2010), Applied Physics Letters, 105, 242407 (2014), Physical Review B 86, 024426 (2012), and IEEE Trans Magn., Vol. 46, No. 6, 2086 (2010)). In general, the TMR element has higher element resistance than the GMR element, whereas a magnetoresistance (MR) ratio of the TMR element is greater than that of the GMR element, TMR elements can be classified into two types. The first type is a TMR element that uses only a tunnel effect using a proximity effect of a wave function between ferromagnetic layers. The second type is a TMR element that uses a coherent tunnel that uses conduction of a specific orbit of a non-magnetic insulating layer to be tunneled when the tunnel effect occurs. It is known that the TMR element using the coherent tunnel obtains an MR ratio greater than that of the TMR element using only the tunnel. The coherent tunnel effect is induced when a ferromagnetic layer and a non-magnetic insulating layer are crystalline, and when an interface between the ferromagnetic layer and the non-magnetic insulating layer is crystallographically continuous.
Magnetoresistance effect elements are used for various purposes. For example, a magnetoresistance effect type magnetic sensor is known as a magnetic sensor, and the magnetoresistance effect element fixes characteristics of the magnetic sensor in a playback function of a hard disk drive.
The magnetoresistance effect type magnetic sensor is a magnetic sensor that detects an effect of a direction of magnetization of the magnetoresistance effect element being changed by a magnetic field from the outside as a change in resistance of the magnetoresistance effect element.
According to IEEE Trans Magn., Vol. 46, No. 6, 2086 (2010), it is known that highest playback capability is obtained when a resistance area (RA) of the magnetoresistance effect element ranges from about 0.1 to 0.2 Ω·μm2 in view of a high frequency response in a magnetoresistance effect type magnetic sensor for detecting a magnetic field of a micro region typified by a magnetic head.
A device expected in the future is a variable magnetoresistance random access memory (MRAM). The MRAM is a memory that adequately changes ferromagnetic directions of two layers in parallel and antiparallel and reads magnetoresistance into digital signals of 0 and 1.